Python 异步IO取消错误和键盘中断
我正在尝试两种方法来阻止无限循环运行:Python 异步IO取消错误和键盘中断,python,python-asyncio,Python,Python Asyncio,我正在尝试两种方法来阻止无限循环运行: 主管\u 1:按程序取消任务 主管2:使用Ctrl+C停止任务 虽然supervisor_2在中断时不会抛出任何错误,但我无法从获取中获取supervisor_1任务已被销毁,但它处于挂起状态。知道为什么吗 代码如下: import asyncio import aioredis from functools import partial class Listener: def __init__(self, redis_conn):
- 主管\u 1:按程序取消任务
- 主管2:使用Ctrl+C停止任务
中获取supervisor_1任务已被销毁,但它处于挂起状态代码>。知道为什么吗
代码如下:
import asyncio
import aioredis
from functools import partial
class Listener:
def __init__(self, redis_conn):
self.redis_conn = redis_conn
async def forever(self, loop_name):
counter = 0
try:
while True:
print('{}: {}'.format(loop_name, counter))
counter += 1
await asyncio.sleep(1)
except asyncio.CancelledError:
print('Task Cancelled')
self.redis_conn.close()
await self.redis_conn.wait_closed()
async def supervisor_1(redis_conn):
redis_conn = await redis_conn
l = Listener(redis_conn)
task = asyncio.ensure_future(
asyncio.gather(l.forever('loop_1'),
l.forever('loop_2')))
await asyncio.sleep(2)
task.cancel()
async def supervisor_2(redis_conn):
redis_conn = await redis_conn
l = Listener(redis_conn)
await asyncio.gather(l.forever('loop_1'),
l.forever('loop_2'))
if __name__ == '__main__':
redis_conn = aioredis.create_pool(('localhost', 5003), db=1)
loop = asyncio.get_event_loop()
run = partial(supervisor_2, redis_conn=redis_conn)
task = asyncio.ensure_future(run())
try:
loop.run_until_complete(task)
except KeyboardInterrupt:
print('Interruped !')
task.cancel()
loop.run_forever()
finally:
loop.close()
@更新:
感谢@Gerasimov,这里有一个版本可以解决这个问题,但不知何故仍然会不时在键盘中断上出现错误:
async def supervisor(redis_conn):
redis_conn = await redis_conn
l = Listener(redis_conn)
task = asyncio.ensure_future(
asyncio.gather(l.forever('loop_1'),
l.forever('loop_2'))
)
await asyncio.sleep(10)
task.cancel()
with suppress(asyncio.CancelledError):
await task
async def kill_tasks():
pending = asyncio.Task.all_tasks()
for task in pending:
task.cancel()
with suppress(asyncio.CancelledError):
await task
及
task.cancel()
本身并没有完成任务:它只是告诉task应该在其内部引发canceledError
,并立即返回。您应该调用它并等待任务实际被取消(同时它将引发cancelederror
)
您也不应该在任务内部抑制cancelederror
阅读我试图展示处理任务的不同方式的地方。例如,要取消某些任务并等待其取消,您可以执行以下操作:
from contextlib import suppress
task = ... # remember, task doesn't suppress CancelledError itself
task.cancel() # returns immediately, we should await task raised CancelledError.
with suppress(asyncio.CancelledError):
await task # or loop.run_until_complete(task) if it happens after event loop stopped
# Now when we awaited for CancelledError and handled it,
# task is finally over and we can close event loop without warning.
谢谢你的链接。我用我对补丁的理解更新了我的答案。但是仍然会出错(但不总是像以前一样)@Orelus,还是以前的错误吗?尝试移动循环。在loop.close()之前,运行\u直到\u完成(kill\u tasks())
到finally块中。这可能会解决问题。我不确定您的run()
coroutine会做什么,但当它完成时,可能会发生这种情况,但有些任务并非如此:在这种情况下,在关闭事件循环时,即使未发生键盘中断
,也会收到警告。请注意使用这种方法的一个缺点:如果调用任务本身在等待子任务清理和退出时被取消,则抑制()
调用将取代取消错误
,事实上,等待任务
可能会提前中止。看起来当前的asyncio(至少从3.8开始)可能无法避免这种情况。
from contextlib import suppress
task = ... # remember, task doesn't suppress CancelledError itself
task.cancel() # returns immediately, we should await task raised CancelledError.
with suppress(asyncio.CancelledError):
await task # or loop.run_until_complete(task) if it happens after event loop stopped
# Now when we awaited for CancelledError and handled it,
# task is finally over and we can close event loop without warning.